Cannabis Effects on Driving-related Skills of Young Drivers

This study will test the prediction that residual effects of an acute dose of cannabis on driving-related skills will be observed in a group of young drivers 48 hours following a single dose of smoked cannabis, and will also examine the effects of an acute dose of cannabis on those skills using driving simulator technology.

Study Objectives

• Examine the residual effects of a moderate dose of cannabis (12.5% THC) on driving simulator performance of young drivers. Simulated driving performance, tests of cognition, verbal memory, and mood will be measured concurrently with levels of cannabinoids in biological fluids at approximately 24 and 48 hours following acute drug exposure in male and female drivers aged 19 to 25. We will test the hypothesis that performance on a high-fidelity driving simulator task will be significantly impaired approximately 24 hours following a dose of cannabis in comparison to a placebo condition.
• Examine the acute effects of a moderate dose of cannabis (12.5% THC) on driving simulator performance of young drivers. Simulated driving performance, tests of cognition, verbal memory, and mood will be measured concurrently with levels of cannabinoids in biological fluids before and after drug administration. Cannabinoid levels in biological fluids will be measured over a 6 hour period following drug exposure. We will examine the relationship of cannabinoid levels to performance measures in this time frame.
• Explore the effects of driving history, driving attitudes, and individual difference measures (e.g., demographics, drug and alcohol use, etc.) on the acute and residual effects of cannabis on driving simulator performance of young drivers. Exploratory analyses will be undertaken to determine if the acute and residual effects of cannabis on the driving simulator task are influenced by these measures.
• Determine if a relationship exists between genetics and THC response. As an ancillary aim, blood samples may be collected for future research to determine if a relationship exists between genetic polymorphisms and pharmacokinetic and pharmacodynamic responses to cannabis.

Study Design and Duration

The study is a double-blind, placebo-controlled mixed-design study, including a randomized between-subjects comparison of the effects of smoked cannabis and both between- and within-subjects examination of its residual effects at 24 and 48 hours following one-time drug administration. Although a placebo condition is part of the study, this is not a treatment study.

Initial contact with potential subjects will be made via telephone, and study personnel will conduct a telephone screen for eligibility. Upon eligibility confirmation by telephone, participants will be asked to attend CAMH for an eligibility assessment. The study will consist of 5 sessions for each subject (an eligibility assessment, a practice day, and three subsequent testing days). Participants will be asked not to use cannabis for 48 hours prior to attending the practice day (Session 2). Although Session 1 can be completed at any time prior to the remaining study sessions, Sessions 2 - 5 must be performed on consecutive days.

In certain instances, the Qualified Investigator may ask a participant to return for re-screening, e.g. repeat of urine test or other assessments performed for eligibility assessment. Also, in case of unforeseen delays in scheduling study participation, the Qualified Investigator will determine if there is a need to ask a participant to repeat some assessments, e.g., physical examination.

Inclusion criteria

• Males and females aged 19 to 25
• Regular cannabis users (between one and four times per week)
• Held a valid class G or G2 Ontario driver's license (or equivalent from another jurisdiction) for at least 12 months.
• Willing to abstain from cannabis use for the duration of the study, and for 48 hours prior to Session 2.
• Provides written and informed consent
• Urine toxicology result positive for THC (indicating recent use of cannabis).

Exclusion criteria

• Positive breathalyzer results for alcohol on any given study day.
• Is a regular user of medications that affect brain function (i.e., antidepressants, benzodiazepines, stimulants).
• Diagnosis of severe medical or psychiatric conditions.
• A first degree relative diagnosed with schizophrenia.
• Meets criteria for current or lifetime Substance Use Disorders (DSM-IV) with the exception of nicotine.
• Meets criteria for Cannabis Dependence (DSM-IV).
• Is pregnant, is trying to become pregnant, or is currently breastfeeding.

Ongoing Exclusion Criteria:

• Upon eligibility assessment, toxicology results indicate that the participant has not used cannabis recently.
• Any toxicology screen after Session 2 - Practice Day indicating a psychoactive substance has been used other than cannabis.